Mayor Michael Nutter of Philadelphia was true to his word when he took to the pulpit at Mount Carmel Baptist Church and prefaced his remarks: “I’m going to say some things this morning that I know from time to time many of you think, but may not say. They will not be PC.”

He proceeded to unloose a 25-minute speech that must rank among the most brutally forthright calls for personal responsibility and adult authority that an elected official has ever delivered in these United States.

Philadelphia has been beset by “flash mobs,” roving bands of teenagers who descend on innocent bystanders to beat and rob them in a miniature version of the senseless destruction that has engulfed London. Urban violence always occasions tawdry excuse-making under the guise of a search for “root causes.” With a pungent plain-spokenness, Nutter zeroed in on the true root causes — irresponsible parents and their ignorant, slovenly and undisciplined kids.

“Parents,” Nutter said, “get your act together. Get it together, right now!” On the cusp of officially announcing a new curfew for teens that will bring potential sanctions for the parents of violators, he warned neglectful parents: “You’re going to find yourself spending some quality time with your kids in jail, together.”

And that was practically the warm-and-fuzzy portion of his presentation. He had scorching words for absent fathers in a city with an astronomical black illegitimacy rate: “You’re not a father just because you have a kid, or two, or three.” If you’re not providing moral instruction to your children and instead are sending child-support payments, “You’re just a human ATM.” If you’re doing neither, “You’re just a sperm donor.

“That’s part of the problem in our community,” he continued. “Let me speak plain: That’s part of the problem in the black community.

“We have too many men, making too many babies that they don’t want to take care of, and then we end up dealing with your children,” he said. “We’re not running a big baby-sitting service. . . You were around for the sex — now, be around for the parenting.”

Nutter harkened back to his days as a teen in West Philadelphia 40 years ago, when he lived under the “Basil and Catalina code, the code of my parents.” They set out simple rules — respect others, keep your hands to yourself, mind your manners — and made it clear that as long as he “lived in their house, that was it.”

At the end of his talk, he directly addressed today’s teens in a volcano of indignation that brought parishioners to their feet. “If you want us to respect you,” he thundered, “take those doggone hoodies down, especially in summer,” “pull your pants up and buy a belt,” “comb your hair,” “learn some manners,” “keep your butt in school” and “extend your English vocabulary beyond the few curse words that you know.”

“If you go to look for a job,” he continued, “don’t go and blame it on the white folks or anyone else if you walk into somebody’s office with your hair uncombed and your shoes untied or your pants half down, tattoos up and down your arms, on your face, on your neck. And you wonder why somebody won’t hire you? They don’t hire you because you look like you’re crazy!”

The third African-American mayor in Philadelphia’s history, Nutter is a reformer who took over from an incompetent predecessor who blithely presided over murder-plagued “Killadelphia.” He inveighs against vast social trends. The unraveling of the two-parent family and the diminution of adult authority go back decades. Nutter may be able to beat back the flash mobs, but the larger social disaster that is the context of such mayhem will endure.

At least he is willing to speak about the desperate need for a return to basic standards. That Nutter’s speech is refreshing and brave is itself a disturbing sign of the times.